Denticetopsis sauli Ferraris, 1996

Vari, Richard P., Ferraris Jr, Carl J. & de Pinna, Mário C. C., 2005, The Neotropical whale catfishes (Siluriformes: Cetopsidae: Cetopsinae), a revisionary study, Neotropical Ichthyology 3 (2), pp. 127-238 : 217-218

Denticetopsis sauli Ferraris, 1996

Figs. 46 , 52 , Tables 16-22

Denticetopsis sauli Ferraris, 1996: 164 , figs. 3, 11 [type locality: Venezuela, Estado Amazonas, outflow stream from series of morichales, ca. 5.0 km from mouth of río Pamoni, 2°48’N, 65°53’W].– Taphorn et al., 1997: 85 [ Venezuela].– Evers & Seidel, 2002: 741 [listing].–Vari & Ferraris, 2003: 258 [in check list, distribution].

Diagnosis. Denticetopsis sauli is distinguished from all of its congeners with the exception of D. royeroi by the combination of the possession of elongate, symphyseal teeth on the dentary, a reduced lateral line not extending posteriorly on the body beyond the abdomen, an edentulous vomer, a dorsal fin with only 4 segmented rays and without a spinous first fin ray, an obliquely-truncate margin on the caudal fin, and the lack of horizontally-elongate, stellate, dark chromatophores when the chromatophores are expanded. Denticetopsis sauli is distinguished from D. royeroi by the posterior extent of the margin of the maxilla (extending at least one eye diameter past the posterior margin of the orbit versus extending only slightly beyond the posterior margin of the orbit, respectively), the body depth (17.1-19.5 of SL versus 23% of SL, respectively), and the extent of the membranous connection between the caudal and anal fins (membrane distinctly incised versus without a distinct notch, respectively).

Description. Body moderately-elongate, slightly transverselycompressed anteriorly, becoming increasingly compressed posteriorly. Body depth at dorsal-fin origin approximately 0.20 of SL and equal to length of postorbital portion of head. Lateral line canal incomplete, interrupted, and restricted to abdomen. Dorsal profile of body straight and very slightly inclined from nape to dorsal-fin origin; nearly straight from dorsal-fin origin to caudal-fin base. Ventral profile of body convex along abdomen, approximately straight, but very slightly posterodorsallyslanted along base of anal fin. Caudal-peduncle length slightly less than one-half of caudal-peduncle depth.

Head acutely triangular overall in lateral view but somewhat rounded anteriorly. Dorsal profile of head slightly convex from tip of snout to posterior nares and straight from nares to posterior of nape. Ventral profile of head gently convex. Profile of snout in dorsal view broadly rounded. Portion of head posterior of nares with lateral profiles extending nearly in parallel from dorsal view. Dorsal surface of posterior portion of head without externally apparent enlarged jaw musculature present in many species of Cetopsinae .

Opercular membrane only slightly attached as far posteriorly as vertical through posterior margin of orbit. Opercular opening very wide; extending dorsal of pectoral-fin insertion by distance approximately equal to eye diameter and anterior of pectoral-fin insertion for distance equal to approximately one-half of HL.

Eyes situated on lateral surface of head; located entirely dorsal to horizontal extending through pectoral-fin insertion; eye visible in dorsal view, but not in ventral view, of head. Middle of orbit at slightly less than anterior one-third of HL. Eye diameter between one-third and one-half of snout length. Interorbital width approximately equal to distance from tip of snout to middle of eye. Anterior narial opening circular, surrounded by short, anteriorly-directed, tubular rim of skin. Opening of anterior nares located at horizontal extending through tip of snout and slightly dorsal to horizontal extending through maxillary-barbel origin. Distance between anterior nares much greater than distance from anterior to posterior nares, and approximately equal to distance from tip of snout to posterior margin of orbit. Posterior narial opening large, located near dorsal profile of head, and within region between verticals through anterior margin and middle of eye. Opening round, with anterior portions of aperture bordered by flap of skin; flap highest anteriorly. Distance between posterior nares slightly less than distance between anterior nares.

Mouth inferior; its width approximately two-thirds of HL. Margin of lower jaw broadly rounded, its posterior extent reaching beyond vertical through posterior margin of eye for distance equal to one eye diameter. Premaxillary tooth patch elongate, continuous across midline; anterior margin convex, posterior margin concave and running in parallel to anterior margin. Teeth in upper jaw small, conical, and sharply-pointed, with teeth arranged in two rows at symphysis and reduced to one row laterally. Teeth of both rows of approximately same size, except for two or three, enlarged teeth located at lateral limit of premaxilla. Vomerine teeth absent. Dentary with single row of small, conical teeth extending from base of coronoid process midway to symphysis and with second tooth row located anterior to, and along, lateral portion of primary tooth row. Oral surface of dentary at symphysis expanded medially and bearing irregular patch of large, conical teeth. Smaller teeth of primary dentary tooth row located anterior to enlarged teeth situated proximate to dentary symphysis.

Maxillary barbel slender, its length distinctly greater than distance from tip of snout to posterior margin of orbit and approximately equal to one-half of HL; barbel origin located near vertical through anterior margin of orbit. Mental barbels approximately equal in size to, but slightly shorter than, maxillary barbel. Medial mental-barbel origin located along vertical through middle of orbit. Lateral mental-barbel origin located slightly posterior of vertical through posterior margin of orbit. Tips of adpressed mental barbels falling short of posterior margin of opercle.

Dorsal fin moderately large overall with length of dorsalfin base approximately 0.22-0.26 of HL and equal to distance from tip of snout to middle of orbit. Length of longest dorsalfin ray equal to slightly less that one-half of HL. Dorsal-fin spinelet absent. First dorsal-fin ray spinous for basal onehalf, ray segmented and flexible distally and without distal filament. Distal margin of dorsal fin slightly convex, with second branched ray longest. Dorsal-fin origin located at approximately anterior one-third of SL and along vertical through middle of adpressed pectoral fin. Tip of adpressed dorsal fin reaching to vertical through anal-fin origin. Posterior most dorsal-fin ray without posterior, membranous attachment to body.

Caudal-fin margin obliquely-truncate with dorsal principal-fin rays longest. Length of dorsal most principal caudalfin ray approximately 1.5 times length of ventral most fin ray.

Base of anal fin long, approximately 0.40-0.41 of SL. Analfin origin located approximately along vertical through middle of SL. Anal-fin margin nearly straight, with all rays of approximately equal length. Posterior most anal-fin ray with posterior, membranous attachment along one-half of its length to ventral most procurrent caudal-fin ray. Anal and caudal fin margins largely continuous, but separated distally by small notch.

Pelvic fin short, distal margin convex, middle fin rays longest. Pelvic fin located entirely anterior to vertical through middle of SL, with its origin along vertical through middle portion of base of dorsal fin. Tip of adpressed pelvic fin falling slightly short of anal-fin origin. Medial most pelvic-fin ray with membranous attachment to body for basal one-fourth to one-third of its length.

Pectoral-fin length approximately one-half of HL. Pectoral-fin margin very slightly convex, with middle fin rays longest. First pectoral-fin ray spinous, but flexible distally and without either serrations or distal filament.

Coloration in alcohol. Dark pigmentation on head and lateral surface of abdomen largely in form of scattered, stellate, dark chromatophores of approximately size of eye when fully expanded but with chromatophores constricted in many specimens (e.g., Fig. 52 ). Chromatophores on posterior region of body noticeably smaller. Body light brown in specimens with fully-expanded chromatophores and creamy white with fine, brown spots in specimens with contracted chromatophores. Caudal region with dark chromatophores evenly distributed other than for denser concentration of spots along dorsal midline and along base of caudal fin. Chromatophores less concentrated above base of anal fin and on ventrolateral surface of abdomen. Humeral region of body with more densely concentrated patch of dark chromatophores forming diffuse, triangular blotch extending posteriorly in some individuals as far as length of adpressed pectoral fin. Dorsal and lateral surfaces of nape, snout, and dorsal portion of head as far ventrally as horizontal extending through orbit with few, scattered, dark chromatophores. Remainder of head and abdomen with few, if any, widely-scattered, dark chromatophores.

Dorsal fin with dark spot no larger than size of eye located on base of two anterior fin rays. Pectoral, pelvic, and anal fins lacking dark chromatophores. Caudal fin dusky, with small, dark chromatophores scattered irregularly along both margins of fin rays.

Barbels unpigmented or with few, dark chromatophores basally.

Sexual dimorphism. The limited available sample of Denticetopsis sauli does not demonstrate the sexual dimorphism of the pectoral, dorsal, and anal fins that is present in many species within the Cetopsinae , albeit not in the other species of Denticetopsis .

Distribution. Denticetopsis sauli is only know from the río Pamoni in the río Casiquiare basin of the upper río Negro system of Venezuela ( Fig. 46 ).

Remarks. The largest available specimen, 21 mm SL, is a mature male ( Ferraris, 1996: 167).

Material examined. 7 specimens (17-21.0 mm SL). Venezuela. Amazonas: outflow stream from a series of morichales (palm swamps), approximately 5 km from mouth of río Pamoni, río Casiquiare basin (2°48’N, 65°53’W), MBUCV V-20300, 1 (20.5, holotype of Denticetopsis sauli ); MBUCV V-20301, 2 (20-21; paratypes of Denticetopsis sauli ); ANSP 161432, 4 (17-21; paratypes of Denticetopsis sauli ; 2 specimens, 20-21 mm, cleared and stained).

Figures

Fig. 46. Map of central and northern SouthAmerica showing geographic distribution of Denticetopsis epa (1 = holotype locality), Denticetopsis iwokrama (2 = holotype locality), Denticetopsis macilenta (3 = holotype locality of Hemicetopsis macilenta), Denticetopsis praecox (4 = holotype locality), Denticetopsis royeroi (5 = holotype locality), Denticetopsis sauli (6 = holotype locality), and Denticetopsis seducta (7 = holotype locality) (some symbols represent more that one locality and/or lot of specimens).

Fig. 52. Denticetopsis sauli, paratype, ANSP 161432, 16.5 mm SL; Venezuela, Amazonas, outflow stream from a series of morichales (palm swamps), approximately 5 km from mouth of río Pamoni, río Casiquiare basin (2°48’N, 65°53’W).